1. Field of the Invention
The present invention relates to small internal combustion engines of the type having a closely positioned fuel tank, and that are used to power outdoor implements such as mowers, tillers, lawn vacuums, weed trimmers, snow blowers, water blasters and the like. More particularly, the present invention relates to an improved safety fuel tank and filler cap apparatus that disallows removal of the fuel filler cap portion of the apparatus from the fuel tank when the engine is too hot, such as above a selected safe threshold value.
2. General Background of the Invention
The flash point of a liquid such as gasoline should not be confused with the temperature necessary to ignite the vapors, for unless a source of heat considerably hotter than the flash point of the fuel comes into direct contact with the vapors, the fuel will merely give off vapors without burning. An essential factor in the process of combustion is oxygen. Without oxygen, even the most flammable vapors will not burn. Under normal conditions, a flame draws the amount of oxygen necessary to sustain combustion from the air. When the oxygen content of the air falls below about 15%, there is an immediate extinguishment of practically all flames. There is a wide temperature difference between the flash point of a fuel and the ignition temperature. For example, the flash point (vapor given off) of gasoline is minus 43 degrees centigrade (minus 45 degrees fahrenheit), and the ignition temperature (heat necessary to ignite the mixture) is 257 degrees centigrade (490 degrees fahrenheit). A small flame can be drawn into lube oil which is at average room temperature and it will not burn, but with the addition of burning gasoline, vapors soon rise and burn to raise the temperature of the surrounding oil to the flash point.
Every year, fires cause serious and sometimes fatal bodily injury to operators of small outdoor or yard and garden implements such as lawn mowers, lawn vacuums, weed trimmers, water blasters and the like. One of the most common safety problems is associated with the attempt by individuals to add gasoline to the internal combustion engine of a lawn mower or like implement that is still running. Sometimes, an implement gradually loosens the gas filler cap because of vibration. Typically, these implements position the fuel tank and its filler neck very close to the engine block. Fuel that spills from the fuel tank or when filling the tank may come into contact with hot surfaces on the engine block or accessories. If the user is not paying close attention to the gas tank and its filler cap, gasoline can begin to leak when the cap is loosened. This problem is especially acute with rear drive type implements such as go-karts, riding lawn mowers and lawn tractors wherein the gasoline tank may be behind the operator or underneath a seat or hood preventing the user from seeing it. Many tractor style riding lawn mowers have such a hidden fuel tank and filler cap.
Many of these implements are operated by adolescent children that are not fully informed by their parents about the danger of filling fuel tanks with gasoline when the vehicle engine block is hot from operation.
Many manufacturers use decal warning stickers and user's manual warnings to warn a user to not remove the fuel filler cap until the engine cools for at least a couple of minutes. Despite such warnings, many users have a bad habit of smoking when operating such an implement, so that if the cap loosens, the operator does not notice the escape of fumes if the engine continues to run.
Generators are often filled when running because the user does not want to interrupt the flow of electricity.
All of these situations are hazardous if the engine continues to run when the filler cap is removed.